Handling 'Cache data was lost' Error on Server Startup

Symptom:

Servers equipped with write-back cache SAS RAID cards, including ThinkSystem, System x, and ThinkServer series models, display a "Critical Message" error stating "Cache data was lost..." during the boot process.

Note: The error interface may vary across different server series models.

Cause Analysis:

When a SAS RAID card with write-back cache performs write operations, data passes through the RAID card cache before being written to the hard drives. If the server loses power before the data is fully written to the drives, the unwritten portion in the cache may be lost. Upon powering on the server again, the RAID card's self-check detects incomplete data writes, triggering this error.

Any abnormal shutdown can cause this issue, including:

1. Power outage;

2. Manual forced shutdown;

3. Server crash.

Loss of array controller cache data may cause operating system errors or file corruption. In severe cases, it can lead to array errors, disconnection, or the RAID card entering safe mode.

Solution:

When the cache data loss error occurs, you typically must ignore the message and are advised to check the RAID status first. The specific steps are as follows:

On the "Critical Message" screen, move the cursor down to "Enter Your Input Here:", press Enter, type the letter "A" in the input box, and then press Enter again;

You will then see the message "Critical Message handing completed. Please exit." After processing is complete, press the ESC key to exit;

Next, press the letter "Y" key to continue;

The server will then continue the POST and boot process. It is recommended to enter the RAID card configuration interface at this time to verify the RAID status. If the RAID status is normal, you can proceed with normal booting.

If the system fails to boot or reports errors, it may be caused by cache data loss, requiring system repair or reinstallation.

If the "Critical Message" prompt reappears after shutting down or rebooting following the above steps, a hardware failure may have occurred. Contact after-sales service for repairs immediately.

Solutions to reduce the occurrence of cache data loss issues:

1. Set the Virtual Drive Write Cache Policy to Write Through (direct write mode). Note that this mode significantly reduces RAID performance, especially for RAID 5 and RAID 6;

2. Install additional batteries (BBU) or flash backup units (Flash Backup Write Cache and Super Capacitor);

3. Equip with an UPS (Uninterruptible Power Supply).